When 26 Doesn’t Equal 26
Don’t Let Camera Megapixels Fool You
For a non- or semi-technical person, when it comes to megapixels (or pretty much anything), the common understanding is that bigger is better. But there are caveats. Aren’t there always? (Wine and chocolate come immediately to mind).
The following is a brief and elementary explanation of camera resolution and what to look for when you’re purchasing a scanner as it pertains to this topic. It’s important to note that this is just one factor of many, albeit an important one.
Megapixel: TechTerms.com gives a good lay description of megapixel, stating, “A megapixel is one million pixels. It is commonly used to describe the resolution of digital cameras. For example, a 7.2 megapixel camera is capable of capturing roughly 7,200,000 pixels. The higher the megapixel number, the more detail the camera can capture.”1
Image Sensor: The part of the camera that converts the image into digital pixels.
Resolution: Scanner resolution is measured in dots per inch (dpi). In general, the greater the dpi, the better the image clarity.
Spatial Resolution: The measure of how closely lines can be resolved in an image is called spatial resolution and it depends on properties of the system creating the image, not just the pixel resolution in pixels per inch (ppi) [or dpi]. For practical purposes, the clarity of the image is decided by its spatial resolution not the number of pixels in an image.2 What this means is that an image with a higher pixilation but lower spatial resolution will be more blurry than an image with a lower pixel count but a higher spatial resolution.
Optical Resolution or True Optical Resolution: The built-in resolution of a scanning device. Contrasts with “interpolated resolution” or “digital resolution,” which enhances an image by software. Both resolutions are given as dots per inch (dpi)…a 2,400 dpi scanner can be the true resolution of the machine or a computed resolution.3
Interpolated Resolution: An enhanced resolution of a scanning device that is computed using a software algorithm. Also called the “digital resolution,” it makes an image appear as if it were scanned at a higher resolution. An interpolated resolution is considerably greater than the optical resolution, which is the inherent physical resolution of the device. Depending on the contents of the image and the scanning algorithm, an interpolated, or enhanced, resolution can improve or degrade the original.4
Got all that?
With all of this new found (or reminded) knowledge, we recommend that one of the questions to ask when purchasing a scanner is “What is the true optical resolution of the camera?”
Recently, a competitor has touted a 26 megapixel camera, literally blowing away the entire field of competitive offerings…but only for those who don’t understand the definitions above. In reality, the scanner uses a 6.6 megapixel image sensor that captures a number of separate images (for approximately 26 megapixels), restructuring them into a single final image. This could result in a lack of necessary spatial resolution and a potentially degraded image with restructuring artifacts. While the competitive unit is well-respected and provides a quality image, it does not have a 26 megapixel camera. In this instance, the true optical resolution is actually 6.6 megapixels which is less than the cameras of other units on the market.
As stated in the opening, camera resolution is just one factor to study when making a purchase. Don’t let the numbers fool you; be knowledgeable.
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If you have any questions or comments about the importance of true optical resolution in scanners or are interested in capture equipment or scanning services, please contact The Crowley Company by calling (240) 215-0224. General inquiries can be emailed to [email protected]. Please also follow The Crowley Company on Facebook, Twitter, Google+, LinkedIn, Pinterest, and YouTube.